Method and apparatus for heat treating and sintering



Jan. 27, "1942.

J. S. PECKER EI'AL METHOD AND APPARATUS FOR HEAT TREATING' AND SINTERING5 Shee ts-Sheet V 1 Filed June 22, 1940 9 J. S. PECKER- ETAL METHOD ANDAPPARATUS FOR HEAT TREATING; AND SINTERING Filed June 22, 1940 5 $heetshe et 2 SEPH S. E SR5: HENRY A.$IM P$ON ATTORN EY Jan. 27, 1942'. .1. s.PECKER EI'AL METHOD AND APPARATUS FOR HEAT TREATING AND SINTERING FiledJune 22, 1940 5 Sheets-Sheet 3 C R 8r MPSON JOSEPH s. HENRY A. 5| W wA'I'TORNEY 5 Sheets-Sheet 4 J. 5. PECKER .ET AL Filed June 22, 1940METHOD AND APPARATUS FOR HEAT TREATING AND SINTERING JOSEPH $.PECKER a:HENRY A. SIM

Jan- 7, 914 J. s. PECKER ETAL 2,271,091

METHOD AND APPARATUS FOR HEAT TREATING AND SINTERINU Filed June 22, 19405 Sheets-Sheet 5 INVENTORS JOSEPH S. PECKER 8r HENRY AISIMPSON BY W WATTURN EY Patented Jan. 27, 1942 i ivmrnon AND APPARATUS ron near ,zrnssrmcAND snvrnnme Joseph 'S. Pecker and Henry A. Simpson, Philadelphia, Pa.,assignors to Machine and Tool Designing 00., Philadelphia, Pa., acorporation .0! Pennsylvania Application June 22, 1940, Serial No.341,830

' 7 Claims.

This invention relates to a method and apparatus for a heat treating,sintering or welding system for the handling of metal objects or unitsespecially those which have been formed from metallic powders, orincombination with chemicals and intended to be subjected to an atmosphere of inert gases, and has for a. purpose to provide compact,convenient and eflicient means for sintering, sintering and cooling, orsintering at varying temperature the materials during their continuoustraverse through the system.

A further purpose is to provide a novel design for a sintering systemwherein the total space occupied is of a greatly reduced area incomparison with plants and methods in use at the present time toaccomplish similar purposes.

- A further purpose is to provide a continuous vertical helical trackwayhaving a descending and an ascending path for the guidance of individualconveyors and a propelling means for controlling the movement of theconveyors both down and up the path of the trackway.

A further purpose is to provide two separate chambers,-one within theother, one for heating purposes and the other for cooling, and having acontinuous vertical helical trackway passing through one chamber toprovide an in-feed, and crossing to the other chamber to provide anoutfeed.

A further purpose is to provide conveyors in the form of individual carshaving wheel'trucks with separable container bodies supported there- 'onand adapted to roll freely over the tracks of the helical trackway, thebodies being formed of perforated material to permit of a freecirculation of heat and/or cold, having provision for quick andeflicient mounting and demounting upon and from the wheel trucks, andtrays of similar perforated material adapted to interlock in stackformation and to fit within the demountable bodies.

A further purpose is to provide a stationary insulated outer casing toform one of the chambers and an inner rotatable shell to form the otherof said chambers, the rotatable shell carrying a propelling means forthe individual conveyor cars and also acting to keep said cars in properspaced relation during their traverse of the spirals.

' A further purpose is to provide sealed compartments with dual sets ofdoors for the intro-,

duction and ejection of the conveyor cars, whereby the escape of heat,gases, etc. are minimized.

A further purpose is to provide the introduction compartment with doorcontrolling mechanism, operable from and in timed relation to therotating propelling means and whereby both sets of doors cannot beopened at the same time.

A further purpose is to provide'one or both of the chambers withelectric heating elements of helical or other formation so arranged asto follow the path of the conveyor cars and to re- 10 fiect heat thereonfrom above, below and from each side throughout the entire traverse ofeach car and to provide proper circuits for energizing the elements,either wholly or in part, in either one or both of the chambers andproper controls for same.

A further purpose is to provide one of said chambers with a controlledcooling means preferably in the form of circulated cooling medium whichcooling is caused to function when but one of the chambers is used forheating.

A further purpose is to provide glazed openings ,at convenient points inthe walls forming both chambers whereby visual inspection of thematerials under treatment can be made.

A further purpose is to provide valve controlled means for theintroduction of gases, and circulating means for retarding the escape ofthe gases through doors of entrance and exit compartments.

ture for the support of the respectiv casings forming the separatechambers, the helical trackway therein, the helical heating elements,and to further provide means for rotating the walls forming the innerchamber at variable speeds.

Other purposes and attendant advantages will become readily apparentfrom the accompanying specification and illustrated embodiment of oneform of our invention, reference to which readily apparent.

It has been the practice in the past in the art of sintering objectsformed of compressed powdered metals to introduce containers to and movethem through insulated chambers of great length, as the sinteringprocess is slow and requires much time. The cost of apparatus of thisnature was necessarily high as well as the cost of maintenance, and thetreating process comparatively slow. It is an object of the presentinvention to provide a compact device, wherein the necessary time forheating and time for cooling can be adequately provided within one'andthe same housing and wherein economies of space and thereby initialcosts can be effected.

A further purpose is to provide suitable strucwill make the' above andother purposes more The designof applicant's furnace lends itselfadmirably to mass production, due to its great,

stantially on the line 22 of Fig. 1.

Fig. 3 is an enlarged sectional detail taken on line 3-3 of Fig. 1,illustrating the doors leading from the entrance compartment to theheating chamber and showing mechanism for locking and unlocking. I

Fig. 4 is a sectional detail on the same scale as Fi .3 and taken online 4-4 thereof, showing mechanism for preventing the opening of oneset of doors when the second set is free to open.

Fig. 5 is a sectional plan taken on line 55 of Fig. 2 illustrating thecrossing where the cars are inoved from the inner to the outer chamber,the end of the down helix and the beginning of the up helix.

Fig..6 is an enlarged detail showing in plan the section of track at thepoint of crossover from one chamber to the other and. illustrating indetail the switchinggof segments of track by the car propellingmechanism.

Fig. '7 is a sectional elevation of Fig. 6 taken on line 'l-l thereof,and

Fig. 8 is an enlargedsectional detail, taken-on line 8-8 of Fig. 6,illustrating a'spring tensioned pivot upon which the rail segmentsoperate.

Fig. 9 is an enlarged detail of a vertical section' corresponding to afragment of Fig. 2, and

showing'a conveyor car truck with a detachable "body mounted thereon andcontaining 'a nesting of trays for supporting articles to be sintered.

Fig. 10 is a view partly in side elevation and partly in section of oneend of a conveyor car as shown in Fig. 9.

Fig. 11 is an enlarged sectional detail of one of the nesting trays usedin supporting th articles to be sintered, one side of the view showingarticles positioned at random.

Fig. 12 is a similar view to Fig. 11 showing two of the trays nestedtogether and at one side articles uniformly positioned for sintering.

The cylindrical shell I8 is rotatable, being provided with a suitablerack H! at its base designed to mesh with a motor driven pinionconnected with any suitable source of power (not shown). The base of theshell is also guided in a. suitable cylindrical guide 2| and its freemovement is furthered by means such as a roller hearing or the likeindicated at 22.

Aflixed to the inner face of the outer casing ill and within the chamberB is a plurality of supporting brackets 25. These brackets are soarranged as to support the trackway I 5 in a helical path, performing asimilar function to that of arms M. It will be understood, however, andby reference to the drawings, that the arms 14 support the trackway insuch manner as to'provide a downward helix within chamber A and thebrackets 25 are so arranged as to provide an upward helix of thetrackway within chamber B.

The trackway l5 comprises a continuous two rail track upon whichconveyor cars 26. are propelled. Each of these cars is provided Withsuitable wheel trucks and have detachable body portions 21, the bottomand sides of which are formed of perforated metal, wire mesh or thelike, to provide for a free circulation there-- through.

As the sizes and shapes of the articles to be sintered are of greatvariety and-the shapes infiuence the individual treatment, we furtherpro-. vide trays 21A for use in connection with the body portions 21.These trays are also made of perforated metal or thelike for the samereason the body is perforated, and are designed to nest one aboveanother and fit within the confines of said bodies.

In some instances, the shapes of the articles are such that they may beloosely piled at random within a tray as shown in Fig. 11 and are bestsintered in this formation; in others, the articles must be carefullyplaced and arranged ina uniform manner with free circulation entireabout them, in order that'they be sintered to the best advantage, asshown in Fig. 12.

In still other treatments,. a preliminary subjection to a liquid bath isdesirable, for, which purpose a conveyor having suspended hooked mem-Fig. 13 is an electric diagram illustrating the controls for the heatingelements in both chambers, the cooling mechanism, and the drivingmechanism; theheating elements being shown detached.

Referring now to the drawings, 10 indicates the outer stationary casingof a cylindrical housing, having a tightly closed top H and a tight fora vertical cylindrical shell l8. shell forms the wall for an innerchamber A and is so spaced in its relation to the outer-casing III as toprovide an outer, chamber B entirely around the chamber A.

here can be utilized for engaging certain of the openings provided inthe trays, as shown in Fig. 11; the trays being transported, immersedand stacked or nested by this means. In each case, however,thebody'portions either with or without the trays are mounted upon theconveyor cars 26 for transportation through the chambers.

The propelling means for these cars is provided in the form of a seriesof evenly spaced radially projecting fins 28, which project from boththe inner and outer faces of the cylindrical shell l8 in such manner asto engage either the front .or rear of the cars 26 and cause them tomove with the movement of cylindricalshell l8.

The cars are so constructed as to fit within the spaces created betweenfins 28 and'their front and rear ends are curved to cooperate with theaction of said fins in their paths of rotation.

It will be observedthatdue to the smaller diameter of the trackway I 5in chamber A, .the pitch thereof will be greater than that of thetrackway within chamber B, the number of turns being equal, and that dueto this difference a car fed into chamber A for travel down the helix,will be retarded by the speed of travel of fins 28 on the inner face ofshell I8, while the same car when within chamber B and duringitspathupfore, be seen that the initial feed to theinner chamber A isdesirable, as the smaller diameter and the greater pitch of the trackwayhere, urges the cars in their downward path and tends to assist themovement of shell I 8, thereby acting to counterbalance the powerrequired to lift the cars up the lesser pitched path of the trackwaywithin outer chamber B of the greater diameter.

The cleaning unit in the present example is situated within the centralcompartment of the tank and comprises four rotary brushes 5, i, I, 8.

Arranged within chambers A and B in such helical formation as to followclosely the path of the cars in their respective travels are locatedaseries of electrical heating elements -3l-32 and 33. These elements areso positioned as to reflect heat upon the top, bottom, and sidesrespectively, of the car bodies as they travel the trackway i5. Theelements 30-3! and 32 are stationary, fixedly supported by the arms l4and brackets 25, while the elements 33 are attached to the inner andouter face of the rotatable shell 18 and move therewith, being providedwith brush contacts for energizing same. Eachof the elements isinterrupted at various points throughout their height to create separatezones of heat energy, and each part of the elements so divided can beseparately energized and controlled from an electric switch board (seeFig. 13).

At the top I l of the outer casing Ill) and formed integral therewith isa compartment 35, provided at its outer end with a pair of inwardlyswinging doors 36 and at its inner end with a second pair of inwardlyswinging doors 31. This compartment-is of sufiicient size to house a carand is designed as a lock against the escapement of heat and gases. Itis of such length as to permit a car to be pushed through and past thefirst set of doors permitting said doors to close before the second setof doors 3? can be opened. Both sets of doors are spring shut in theirclosed po-- sition and, are operated to open by the weight of a loadedcar pushing against them and overcoming the tension of their springs,and are further provided with proper sealing means in the form ofgaskets, etc. to efiiciently prevent the escape of gases...

To further minimize the escape of gas, locking means is provided wherebyonly one set of doors can be opened at the same time( see Figs. 3 and4i) and as it is desirable to coordinate this time with the position ofthe fins during travel in their rotary path, the means for unlocking thedoors' 3i and permitting the infeed of a car to chamber A is designed tobe controlled from the rotating shell l8 carrying the fins 28. To thisend a cam groove 38 is arranged about and close to the upper periphery,and on the inner face of the rotating shell l8, and a roller 39 isdesigned to follow the groove of the cam. This roller 39 is attached tothe lower end of a vertically reciprocating plunger ill which is housedin apart of a fixed partition wall 4|, said partition being arranged inline with cylinder 18 and designed to separate chambers A and B abovethe rotating cylinder.

As cylinder 1 l8 rotates, carrying therewith groove cam 38, roller 39,attached to plunger 60 successively moves the latter down and up as itfollows the path ofthe cam. This plunger is so positioned when up, as tolie in the path of and against the swinging doors 3'l thereby preventingtheir being forced open by, a car within compartment 35, In the downposition, plunger is drawn clear of the doors and pressure of a car uponthem will cause them to open permitting the car to roll down the inclineof the track.

Cam 38 is so shaped as to cause the down movement of plunger 40 at sucha time as to coordinate the in-feeding of a car in proper timed relationto the rotation of cylinder l8 and the subsequent positioning of thatcar between fins 28.

Attached to one face of plunger 40 is one arm of a bell crank 42, thefulcrum for which is attached to the fixed bottom of compartment 35. andits other arm is attached to a rod 43 interposed between one arm of asecond bell crank 44. The bell crank 46 has a pivoted fulcrum attachedthe same as bell crank 52 and its second arm is pivotedly connected to aplunger 45 vertically operable within a guide opening in the. bottom ofcompartment 35. This second plunger is located directly in front of theswinging entrance doors 36 in such manner as to prevent their openingwhen the plunger is in its raised position and to permit the opening ofthe doors when the plunger is lowered.

It will thus be understood that, as cylinder l8 rotates, the cam 38 willcontinuously cause plunger 40 to rise and fall and, through the dualbell crank and rod connection just described, will also impart a likemotion to plunger 45, the parts being so arranged that when plunger 40is in the up position locking doors 31, the 'plunger 45 will be in thedown position, permitting the opening of doors 36, and when the plunger40 is lowered, to permit the opening of doors 31, plunger 45 will beraised to prevent the opening of doors 36.

To further oifset any possibility of a car contacting the top of a fin28 as it descends its helix and assumes its proper relation to said iin,the

tops of each fin of the inner chamber are provided erlypositionedthereby and not derailed.

When the inner helicaltrackway reaches the bottom of chamber A, it iscarried outward through openings 5! provided in the wall of cylindricalshell I8. These openings are of sufilcient height to allow a car to passunder and such passage is made by that ml which is following at the rearof the'car as it moves forward and into contact therewith, propellingthe car across that section of angular track comprising the crossover(Fig. 5) and starting it on the upgrade of the helix in chamber B atwhich time it is engaged by that portion of fin 28 which extends fromthe outer face of the shell. In this position, the car is pushed up, thehelix of the outer trackway by the engaging fin 28, the car tracking upthe helix while its engaging face travels a vertical path against theface of that fin with which it happens to be engaged.

The tracks proper are broken as indicated at 52 (see Figures 5, 6 and 8)and short sections 54 are pivoted at 55in such manner as to be moved bysupports 53 which are integral with the shell 88 as said shell isrotated.

These sections 54 are held normally in line with the rest of the trackby springs 56 which surround the pivots 55 and act to retain them incontact at breaks 52 (see Fig. 6). As the shell [8 rotates, the supports53 successively contact the track sections and swing them upon theirpivots to the dot and dash positions indicated. When the supports passbeyond the sections 54, the action of the springs 56 return them totheir normal (full line) positions, closing the tracks at points 52 toprovide a continuous uninterrupted passage for the following car 26.

When a car has reached the upper limit of its travel in the outerchamber B under the influence of a fin 28, it-is moved over a crest asindicated at 60, Fig. 2, from which point the car moves by gravity overa downwardly inclined length of track 62 and away from engagement withits propelling fin. Arranged in line with this length of track 62 is asecond compartment l (similar to and for a like purpose to compartment35, and two sets of spring tensioned doors 66 and 68 are likewiserespectively provided on entrance and exit ends. These doors aredesigned to swing with the pathof travel of the car and are openedthereby thesame as the doors 36 and 3! in compartment 35. However, nolocking and unlocking mechanism is here required, as the spacing betweencars has already been timed and there is no danger-of both sets of doors66 and 68 being open at one and the same time.

At desirable and convenient points throughout the walls forming bothchambers, there is provided glazed openings 58 for the visual inspectionof the materials under treatment. This is essential as it enables theoperators to properly control the electric heating elements, supplyingheat of the required degree to cooperate with proper sinteringrequirements.

The outer chamber B is provided with suitable cooling means, in thepresent showing diagrammatically illustrated as a motor driven blowerfan 16, supplying air through a duct or ducts I2 to desired pointsapproximate the bottom of the chamber but above the bottom of cylinderl8 so as to prevent the cooling medium from entering the heating chamberA.

A valve controlled pipe for the introduction of gases is indicated at 14leading from a suitable source (not shown) to the bottom of chamber A.

As stated, the entire structure is tightly closed to prevent the escapeof introduced gases, but during the entrance and exit of the carsthrough compartments 35 and 64 respectively, there will be a tendencyfor a portion of the gases trapped in these compartments to escape outof the chambers. To minimize this loss, applicants provide the bottomsof said compartments with openings 13 forming connections with the topof cooling chamber B, and provide the tops of the compartments withother openings 15 communiating with ducts Tl which are in turn piped toI the convenient burners where the gases are disposed of ,by burning.

Gauges 16-46 are conveniently located to indicate temperature in eitherchamber, while at 18 a pressure gauge is shown connected with chamber A.

Referring now to Fig. 13, a diagrammatic view is shown to illustrate theelectric elements of our invention and their various controls.

The heating elements 30, 3| and 32 comprising, together with element 33,the set'in outer chamber B are interrupted at various points 80throughout their respective helical paths, whereby separate heatingareas or zonesare formed, and a wiring connection 8| is supplied foreach zone and leads to a switch board 82. Each connection in the presentinstance is controlled by a switch 83, whereby any one, or all, or anycombinationof zones can be energized.

The element 33, which is attached to the moving shell I8 is furnishedwith a brush contact '84 and are shown as having separate wiringconnections 85 and switch controls 86.

The elements 36-3l and 32 supplying heat to inner chamber A aresimilarly interrupted as in chamber B and wiring connections thereforeare shown at 81 and lead to switches 88 on switchcontacts 89, with wires90 leading to board 82.

Element 33in outer chamber B likewise attached to moving shell I8 isfurnished with brush switches 9| on switch board 92. Each wire BI, 85,81, and 96 where shown in heavy line indicates dual wires. It will thusbe understood that either or both chambers can be heated in theirentirety or the heat in different zones can be varied at will.Applicants recognizethe possibility of a further degree of variation byfurnishing separate controls for each heating element in each zone, or

still further by providing varying degrees of heat to each element bysuch means asgrheostats or the like in' place of the switches shown.

A motor 92 is indicated for driving the inion I 26 through suitablegearing whereby the shell I8 is rotated. This motor is shown connectedby wires 93 to a power source, one wire being subject to the control ofa rheostat 94, whereby the speed of rotation of shell l8 can becontrolled.

Themotor 16 (for driving the blower .fan) is shown connected throughwires 95 to a power source, one wire being subject to'rheostat controlshown at 96, whereby the speed of the fan can be varied and the amountof air supplied to chamber B controlled.

It will be understood that this showing is pure- 1y a diagrammaticillustration of one means of control, and the same may be varied toaccomplish like purposes without departing from the spirit of thisinvention.

doors 36 closing behind each car, before the car itself opens the secondset of doors 31. The dual plungers 40 and acting as looks at this time,prevent the opening of doors 3! if doors 36 are free to open and viceversa, under the control of the rotation of shell l8.

The opening of doors 3! is so timed by the cam 38 as to -allow theintroduction of a car to the top of chamber A in such timed relation asto permit it to assume an initial position between any two inwardlyprojecting fins 28. As the pitch of the trackway of the inner helix issuch as to cause the car to move at a greater. rate of speed than themovement of the fins, the car will engage the rear of one of the finsand be retarded thereby in its downward helical path.

Should the load within the car vary to the extent of changing the speedof the car following its introduction and thereby vary the timedrelation of its engagement with a fin, the cam-like faces at the topsthereof act to either advance the car or retard it and thereby avoidderailing.

during operation, to the top, bottom and both sides of the car' Theheating element located adjacent the paths of travel of the car areproperly energized and heat therefrom is directed body, through theperforations, or orifices of the to create varying zones of difierenttemperatures throughout the heating chamber in accordance with sinteringrequirements ascertained by visual inspection through glazed openings58.

If it is found desirable to prolong the heat treatment for a durationgreater than that provided within chamber A, then the heating elementswithin chamber B are energized and the total travel within both chambersis given to heating, the air flow from the cooling mechanism isdiscontinued, and the cooling is taken care of by conveying the carsover added lengths of trackway outward of the chambers or by dismountingthe bodies 21 and/or trays 21A and stacking them, allowing the sinteredobjects to cool by contact with the normal atmosphere.

Ordinarily the cars and their contents are subjected to controlled,variable heat treatment throughout-the duration of their travel down thehelical path of the trackway, and this time is dependent upon the speedof rotation of the cylindrical shell I8 and its connected fins 28,

which speed can be varied by any well-known mechanism, such, forexample, as rheostat control for the driving motor.

When a car'reaches a point at the bottom of chamber A, it pauses on alevel stretch of track, and the fin with which it has been in contactmoves in advance of the car while the fin following, contacts the rearof the car urging it over the crossing to the outer helix through aregistering opening Si in the bottom of cylinder i8 and starting it onthe upgrade of the outer. helix.

As each car moves from the central chamber A to the outer chamber B, itpasses from the heating to the cooling zone and is preferably subjectedto cooling throughout its entire upward travel of the outer helix.

Upon reaching the top of the helical track, each car is moved over thecrest 60 located at the beginning of the connected tangential length ofdowngrade track leading to the ejection chamber (it. At this point, thecars are switched away from the circular path of the propelling fins dueto their following of the tangential track and again move by their ownmomentum down to and through doors 66, compartment 64 and in someprocesses and wherein the initial high heat treatment is given in onechamber and the subsequent lesser heat treatment in another.

Further attention is directed to the provision for both prolonged heattreatment and even longer time for cooling within a comparatively smallstructure. Assuming the diameter of the entire device to be 14 feet andits height 20 feet, and the diameter of the inner rotating shell 9 feetwhich are the proportions illustrated in Figs. 1-2 and 5 of theaccompanying drawings, the travel of each conveyor would beapproximately180 feet in the central chamber A and 325feet in the outer chamber B.Compare this with any continuous structure wherein over 500 lineal feetof space would be'required', plus space for loading and unloading. Thecondensing of the travel length within a greatly restricted area is alsodesirable as it is a great aid to the required visual inspection,attendants being able to closely observe the physical changes of thematerials being sintered from a few difierent levels as compared withfollowing the travel of the material over a comparatively excessivedistance.

It will be evident that, if for any reason a reversal of theoperation, 1. e. feeding down through theouter chamber and upwardthrough the inner'one, becomes desirable, for other purposes, orreversing the positioningof the heating and cooling hambers or the gasinlet, such change can readily be made without greatly altering thedesign of mechanism here disclosed and without.

departing from the spirit of this invention.

Applicants also recognize the possibilities in employing a singleheating chamber with spiral traverse and allowing the cooling to takeplace naturally in the open. The car bodies 2'! with the treatedmaterials therein can be handled by doors '68 and on to a suitablestopping place (not shown) for unloading the car bodies 2i with thetreated materials, and reloading them for another cycle of operation asjust described.

It will be noted that the individual cars are free to travel through thetwo chambers controlled only by the fins 28, and that the cars may .befed to the device as rapidly as the speed of rotation of'the cylindricalshell will permit.

It has been found that, in sintering certain alloys, 9. much moredesirable product can be obtained in sintering by first subjecting thematerials to a quick heat and then to a gradually reduced temperature.The present design lends itself admirably to this requirement as theinitial heat subjection of the materials is at the top of the cylinderwhere the heat will naturally be the greatest due to it tendency to riseand the subsequent treatment will proceed through an area of graduallylessening temperature.

If it is found-advisable to suit certain conditions, the energizing ofelements in given zones and the de-energizing of them in others, willenable the operator to control the application of heat at varying pointsthroughout either chamber. v

This design will also eliminate the requirement for separate heatingchambers as now employed special mechanisms and stacked for prolongedcooling, or the individual trays 21A in each body can be handled in likemanner.

While the greater portion of this description has been directed tosintering, applicants are fully cognizant of the possibilities of theutilization of the same method and mechanism for other forms of heattreatment of metals, whether preformed from powder alloys or by otherprocesses, such as for example, carbonization, galvanizing, varioushardening treatments,

or, in fact, any treatment of metals requiring subjection to heat,controlled or otherwise, and/or subjected to the action of inert gases.

In view of ourinvention and disclosures, variations and modifications tomeet individual whim or particular need, will doubtless become evidentto others skilled in the art, to obtain all or part of the: benefits ofour invention without copying the structure shown, and we, therefore,claim all such insofar as they fall within the reasonable spirit andscope of our invention in the following appended claims.

We claim:

1. In a device of the character described for heat treating metallicunits, the combinationof means forming two elongated verticallyextending closed chambers, one within the other, means for introducingthe units into thetop of the inner chamber, and for discharging theunits from the top of the outer chamber, helical trackways for carryingthe units from top to bottom of the inner chamber, and from'the bottomto the top of the outer chamber, means for transferri'ng the unitsfromthe bottom of the inner chamber to the bottom of the outer chamberand heating elements associated withthe chambers,

said heating elements being so, disposed as to zones.

diroot the heat to the bottom, sides and top of the units moving in theinner chamber and whereby the heat-arising from said element may beaccumulated at the top of said chamber.

2. In a device of the character described, for heat treating metallicunits, the combination of means forming two elongated verticallyextending closed chambers, one within the other, means for introducingthe units into the top of the inner chamber, and for discharging theunits from the top of the outer chamber, means for carrying the unitsfrom top to bottom of the inner chamber, and from the bottom to the topof the outer chamber, means for transferring the units from the bottomof the inner chamber to the bottom of the outer chamber, and heatingmeans for creating arbitrarily controlledheating zones through which theunits must travel, said heating means comprising a series of electricheating elements and means for connecting each element with a currentsource.

3. In a device of the character described, for heat treating metallicunits, the combination of means forming two elongated verticallyextending closed chambers, for introducing the units into the top of theinner chambenand for discharging the units from the top of the outerchamber, means for carrying the units from top to bottom of the innerchamber and from the bottom to the top of the outer chambe means fortransferring the units from the bottom of the inner chamber to thebottom of the outer chamber, a plurality of electric heating elementsfollowing a path of travel parallel with that of the units, andarbitrarily actuated means for the independent control of theconnections between said electric heating elements and a current source,whereby above-sintering temperature is created and maintained in the topof the inner chamber, de-

rived from the heat arising from the several 4. In a device of thecharacter described, for heat treating metallic units, the combinationofmeans forming two elongated vertically extending closed chambers, oneadapted to rotate within the other, means for introducing the units intothe top of the inner chamber, and for discharging the units from the topof the outer chamber, means tor-carrying the units from top to bottom ofthe bottom to the top for transferring the units from the bottom of theinner chamber to the bottom of the outer chamber, a plurality ofseparately controlled electric heating elements following the courses ofsaid trackways, and glazed windows in the walls of both chambersarranged to come into register one chamber wall rotates from time totime as relatively to the other.

5. In a device or the character described, the

one'within the other, means.

combination of an outer stationary casing closed at top and bottom, aplurality of track supporting' brackets projecting from the casing wallwithin the casing, a centrally positioned vertical stationary supportingcolumn provided with radially projecting track-supporting arms, avertical cylindrical shell supported to rotate between the outer casingand the central column, said shell provided with vertically extendingfins projecting from its inner and outer sides in spaced relationship,an inner helical track supported on said radial arms, and an outerhelical track supported on said brackets, material containers adapted tomove upon said tracks, and adapted .to be actuated by the fins of therotating shell, and electric heating elements carried by the shell andconnected to a source by means of brush connections.

. relationship,

'6. In a device of the character described, the combinationof an outerstationary casing closed at top and bottom, a plurality of track/supporting brackets projecting from the casing wall stationarysupporting column provided with radially projectingtrack-supporting-arms, a vertical cylindrical shell supported to rotatebetween the outer casing and the central column,

" said shell provided with vertically extending fins projecting from itsinner and outer sides in spaced an inner helical track supported on saidradial arms, and an outer helical track supported on said brackets,material containers adapted to move upon said tracks, and adapted to beactuated by the fins of the rotating shell and suitable heating elementsassociated therewith, the heating elements being so disposed as todirect heat to the bottom, the sides and the top of the materialintroduced to and descending the inner chamber and from the of the outerchamber, means inner shell and so that the hottest zone will'be adjacentthe point of introduction of the material to the inner shell.

7. The method of sintering metal powder units, which consists in thefollowing steps, introducing the units into the top of an elongatedvertically extending closed space, causing the downward movement of theunits from the top to the bottom of said space, supplying heat to saidspace to form independently controlled zones of temperature, utilizingportions of the heat supplied to a plurality of zones, in maintaining amaximum temperature in the topmost part of the zone into which thematerial initially enters, then transferring the units into the bottomof a second enclosed space, causing the movement of the units from thebottom a centrally positioned vertical.

